Ropes from monofilaments and process for the production thereof



NOV. 28, 1961 HARTMANN ETAL 3,010,275

ROPES FROM MONOFILAMENTS AND PROCESS FOR THE PRODUCTION THEREOF Filed Aug. 26, 1960 FIG] KARL HARTMANN, HANS SCHM/TTMANN.

A TTO RNEYS' United States Patent I 3,010,275 ROPES FROM MONOFILAMENTS AND PROCESS FOR THE PRODUCTION THEREOF Karl Hartmann, Koln-Stammheim, and Hans Schmittmann, Leverkusen, Germany, assignors toFarhenfabnken Bayer Aktiengesellschaft, Leverkusen, Germany, a corporation of Germany Filed Aug. 26, 1960, Ser. No. 52,118 Clams priority, application Germany Aug. v14, 1958 8 Claims. (Cl. 57-144) The present invention relates to the production of ropes or cords from continuous man-made or synthetic monofilaments, and more particularly to a process for producing such ropes or cords having high tensile strength.

Numerous attempts have been made heretofore to produce ropes of man-made or synthetic monofilaments by the method usually employed in making wire, rope, or wire cable. It was found, however, that the ropes or cables so produced were entirely unfit for use due to the formation of spaces or voids such that the ropes or cables had low tensile strength and binding properties with respect to the individual elements making up the composite rope or cable. In accordance with this method endless monofilaments of synthetic substances, such as plastics, for example polyamides, are spirally disposed about a central core.

Attempts have also been made to produce ropes from man-made or synthetic monofilaments by the method used for making hemp ropes, i.e. in accordance with the hawser laying or cable laying manner. These attempts were also unsuccessful, even in the case of heavy ropes, such as those used for ships, as the ropes produced by this method were entirely too stiff for handling and therefore unmanageable and impractical. By this method a plurality of outer monofilaments are twisted about a central core such that the outer monofilaments are twisted about their individual axes as well as about the axis of the central core. 'Ihese advantageously synthetic monofilament ropes produced in the foregoing manner have only a very low tensile strength, i.e. only about 40% of the initial strength as compared with the values for the individual filaments themselves. This is due to the torsion necessarily imposed on the single filaments during the twisting operation required for producing the strands.

It is an object of the present invention to overcome the above disadvantages and to provide for the produc tion of ropes, cables, and the like from continuous synthetic monofilaments by a process wherein the synthetic monofilaments are converted into strands on wire-rope strand twisting machines in the conventional manner and thereafter laying the strands so formed into ropes by the conventional hemp rope technique.

Other and further objects of the invention will become apparent from a study of the within specification and accompanying drawings in which:

FIGURE 1 is a schematic view partially in section illustrating a stand producing apparatus in accordance with the invention,

FIGURE 2 is a schematic sectional view of a strand formed with the apparatus of FIGURE 1.

FIGURE 3 is a schematic view partially in section of an apparatus for producing a rope or cable in accordance with the invention using strands formed by the apparatus of FIGURE 1, and

FIGURE 4 is a sectional view of a finished-rope or cable produced with the apparatus of FIGURE 3.

In accordance with the present invention, it has been found that an excellent process for the production of ropes, cables, and the like from continuous man-made or synthetic monofilaments may be provided which com-- prises twisting a plurality of individual, outer monofilafilarnents to form a strand, said outer monofilamen-ts being maintained untwisted with respect to their individual axes during said twisting. Thereafter a plurality of such strands are twisted asouter strands about a central core of one such strand maintained in untwisted relation as inner strand to form the finished rope or cable. The outer strands are twisted about their individual axes as well as about the central core inner strand in the second step. In contrast thereto in forming each strand in the first step, the individual outer monofilaments twisted about the central core consisting of untwisted inner monofilaments are in fact maintained in untwisted condition with respect to their individual axes.

Preferably six outer strands are twisted about a seventh central core inner strand to form the finished rope or cable. The central core of untwisted inner monofilaments in each strand is preferably provided as a plurality of parallel plies of continuous single monofilaments, maintained in untwisted condition.

The results obtained in accordance with the production of the strands in accordance with the first step are such that the single monofil-aments during their conversion into strands are not themselves torsioned by twisting about their individual axes and therefore no corresponding diminution of tensile strength occurs. With respect to the second step, by virtue of the positive torsion applied to the plurality of strands, due to the twisting of the strands about their individual axes as well as'about the central core, inner strand, during the laying of the strands into rope form, these strands are accurately superimposed upon one another without the formation of spaces or voids. Consequently, the strands uniformly take up the loads applied to them as a composite unit. Ropes produced in accordance with the invention as described herein are subjected to an average total shortening of the basic material of about 20% as opposed to the 33 /3 shortening resulting from conventional methods used up to the present involving the twisting and laying of common types of filaments into strands and ropes. The stress upon the material during the rope formation in accordance with the process of the invention is essentially less than that which occurs in existing conventional processes. The core and inner layers of the strands themselves in the ropes produced in accordance with the invention are preferably composed of parallel plies of continuous single monofilaments about which the outer monofilaments are laid.

In this way, the load-bearing cross section of each strand is considerably enlarged because the large spaces or voids which inevitably occur in strands made in the conventional manner from round-wire, for instance, are

as a result of the disintegration and-feathering of the 'monofilaments; and

(4) A smaller strand diameter and thereby more favorable weight of the strand with the same tensile strength or increased tensile strength with the same strand diameter.

Preferably one of the following rope constructions is used: 7.x 7; or 7 x19; or 7 X 37.

In breaking or tensile strength tests with ropes produced from man-made monofilaments by the method according to the invention, the tensile strength was measof a plurality of individual monofilaments ured tobe about 83% of that of the initial, untwisted monofilaments.

Referring to the drawing, FIGURE 1 shows schematically the cross section of a known machine used in the method of wireropemanufacture. About a hollow axis 1, a tube 2 rotates in the direction of arrow 3. About the periphery of tube 2, a plurality'of axles 4 are provided rigidly fixed with respect to rotating tube 2. Axles 4 are provided with spools 5 carrying monofilaments 7. Spools 5 are rotatable on axles 4 in the direction shown by arrow 8, i.e. in a counter-clockwise direction when spool 5 is viewed from the side looking toward the left of FIGURE 1.

In the production of a strand in accordance with the invention, a core 6 composed of a great number of capillary monofilaments is continuously drawn off in the direction towards the observer. The core preferably consists of a plurality of parallel plies of individual monofilaments emanating from within hollow axis 1 in untwisted condition. Simultaneously, outer monofilaments 7 are drawn off from the various spools 5 in thesame directionof movement as core 6. While FIGURE 1 only shows one spool carrying a continuous monofilament, it will be 4 instance, outer monofilaments 7, although twisted about the central core 6, are maintained untwisted with respect to their individual axes. (See FIGURE 2.)

It will be seen that if strands producedin accordance with the apparatus shown in FIGURE 1 are thereafter developed into a rope or cable, in accordance with the method involved when using the same apparatus (i.e. FIGURE 1), spaces or voids will be .formed in the finished rope due to the inherent elasticity in the material. Such rope will easily fall apart since the individual strands are not maintained in suitable binding'position with respect to the composite rope.

On the other hand, if the'strands produced according to the wire rope process, with the apparatus of FIGURE appreciated that each of the spools 5 is to be provided a with a continuous monofilament. Outer monofilaments 7 are disposed about core 6 in such a manner that the same wrap around core 6 surrounding the same. During the drawing off of core 6 and outer monofilaments 7, tube 2 rotates in the direction of arrow 3, causing the simultaneous movement of spools 5 relative to axis 1 and core 6. Thus, outer monofilaments 7 are laid spirally about core 6 without the individual outer monofilaments 7 becoming twisted in themselvesfie. monofilaments 7 are maintained untwisted with respect to their individual axes. Accordingly, a strand is formed as shown in FIG- URE 2 which is substantially .free from twist, merely having spirally arranged outer monofilaments 7 disposed along the continuous length of an inner. core 6 of untwisted monofilaments, preferably of capillary dimensions, or at least of much smaller diameter as compared with the diameter of monofilaments 7.

The finished strands produced in accordance with the foregoing operation, therefore, include a core having a cover of outer monofilaments, the same being untwisted with respect to their individual axes.

With respect to FIGURE 3, an apparatus is shown including a rotatable tube '9 movable in the direction of arrow 3 having a plurality of axles 10 revolvably seated on tube 9 by means of transverse axes 12. Spools 11 are rotatably mounted on axles 10 for rotation in the direction of arrow 8 in a similar manner to that of FIGURE 1. Axles 10 and in turn spools 11, therefore, rotate about transverse axis 12, either in the direction shown by arrow 13 or the direction shown by arrow 14. A planetary gear-(not shown) is used for maintaining the rotational movement of axes 12 during the simultaneous rotation movement of tube 9.

Thus, in operation, three movements take place, i.e. the rotational movement of tube 9, and both the rotational movement of spools 11 in the direction of arrow 8 as well as in the direction of either arrow 13 or arrow 14. In this way, the strand 16 which has been formed in accordance with the method of the invention by theapparatus of FIGURE 1 represents the inner strand about which is twisted the plurality of outer strands passing around core 16 during its outward movement from hollow shaft 15, the, outer strands being fed from spools 11 on which they are disposed. The finishedrope or cable is shown in cross section in FIGURE 4 wherein a plurality of outer strands are twisted around a center or inner strand. The outer strands are twisted not only about the inner strand or core but also around their individual axes as well. the other hand, each strand is composed 7 twisted about a centercore 6 of individual capillary filaments. In this 1, are thereafter converted into rope using the strand twisting apparatus shown in FIGURE 3; the foregoing disadvantages are eliminated and a rope is provided free from spaces and voids and solidly disposed in, binding relation with respect to the composite unit, even though the ends of the rope are not specifically and especially tied ofi at the end portions. The apparatus'of FIGURE 3 works in accordance: with the method designated as the conventional hemp rope manufacturing method.

The present invention, therefore, combines the operations, in order, of the wire'rope method for the production of strands and the hemp .rope method for the production of the finished rope from the strands. Due to the self-rotation in the direction of the anrow 13 or 14, the strand twist resulting from the use of the apparatus in FIGURE 3 provides for the shortening of the strand. The number of revolutions of the tube 9 and the individual spools 11 in the direction of the arrow 13 or the arrow 14 are accordingly conveniently correlated to one another such that the shortened length which occurs due to the twisting of theindividual strands is equalized with the length of twist of the rope. twisted together from the individual strands.

In this manner, a useahle, practicalrope of polyamide monofilaments may, therefore, be provided wherein two machines of difierent types are employed in ordinal sequence to first make strands in accordance with the wire rope technique and thereafter to make the finished rope in accordance with the hemp rope technique, in the manner of hawser laying or cable laying.

Were the strands produced. in accordance with the method of wire rope making, and further worked with the use of the apparatus of FIGUREI, the finished ropes would easily fall apart since they would possess insulticient binding of the composite unit. Furthermore, if the polyamide monofilaments were made into strands in accordance with the hemp rope technique employing the apparatus of FIGURE 3 and thereafiter such strands made into rope using the same apparatus in the hawser laying fashion or in the cable laying fashiornthen the ropes produced would possess decreased tensile strength due to the twisting of the individual monofilaments in the stranding as well as in the rope making, in contrast to ropes made from non-twisted individual strands. Where the strands and the finished ropes are both made using the apparatus of FIGURE 3, the same are excessively stifi to the touch, are also unwieldy, and moreover require fixing operations to render them practical.

On the other hand, if the strands of polyarnide monofilaments are produced using'the apparatus of FIGURE 3 in accordance with the hemp rope process and the formed strands thereafter made into rope according to the wire rope technique using the apparatusof FIGURE 1, then, in the same way, duegto the twisting ot'the individual monofilaments in the forming of the stnands, a rope of low tensile strength is produced which has poor binding properties with respect to the composite unit. If this rope is not specially secured at its ends or if the same is not specifically covered alongits entire length or subjected to hardening or fixing procedures, the rope will unravel or fall apart easily. 7

It is only by manufacturing rope in accordance with the present process that the foregoing disadvantages are avoided. This entails the use of the apparatus of FIG- URE 1 for producing strands in accordance with the wire rope technique and thereafter producing the finished rope using the apparatus or" FIGURE 3 in accordance with the hemp rope technique.

This application is a continuation-in-part of copending U.S. application Serial No. 833,157, filed August 12, 1959.

We claim:

1. Process for the production of ropes, cables, and the like from continuous synthetic monofilaments which cornprises twisting a plurality of individual outer monofilaments about a central core to form a strand, said outer monofilarnents being maintained untwisted with respect to their individual axes during said twisting, and twisting a plurality of such strands outer strands about a central core of one such strand maintained untwisted as inner strand to form a rope, said outer strands being twisted about their individual axw as well as about said central core inner strand.

2. Process according to claim 1 wherein six outer strands are twisted about a seventh central core inner strand.

3. Process according to claim 1 wherein the central core of untwisted inner monofilanients includes a plurality of parallel plies of continuous single monofilaments.

4. Process according to claim 1 wherein said monofilaments are polyamide monofilaments.

5. A rope, cable and the like from continuous synthetic monofilaments which comprises a plurality of outer strands twisted about a centrally disposed inner strand, said inner strand being maintained nntwisted with respect to its axis and said outer strands being twisted about their individual axes as well as about said inner strand, each of said strands including a plurality of individual outer synthetic monofilarnents twisted about a central core of untwisted inner synthetic rnonofilaments, said outer monoi'ilarnents being maintained untwisted with respect to their individual axes and twisted with respect to said central core of untwisted inner synthetic monofilaments.

6. Rope according to claim 5 wherein the central core of untwisted monofilarnents includes a plurality of parallel plies of continuous "single monofilaments.

7. Rope according to claim 5 wherein said monofil-aments are polyarnide monofilaments.

8. Rope according to claim 5 wherein six outer strands are twisted about a seven central core inner strand.

References Cited in the file of this patent UNITED STATES PATENTS 2,281,036 Hetzel Apr. 28, 1942 2,343,892 Dodge et a1 Mar. 14, 1944 2,438,864 Reed Mar. 30, 1948 

1. PROCESS FOR THE PRODUCTION OF ROPES, CABLES, AND THE LIKE FROM CONTINUOUS SYNTHETIC MONOFILAMENTS WHICH COMPRISES TWISTING A PLURALITY OF INDIVIDUAL OUTER MONOFILAMENTS ABOUT A CENTRAL CORE TO FORM A STRAND, SAID OUTER MONOFILAMENTS BEING MAINTAINED UNTWISTED WITH RESPECT TO THEIR INDIVIDUAL AXES DURING SAID TWISTING, AND TWISTING 